"Many children, and even adults, dream of visiting other planets and wonder what it would be like to stand on another planet. For one thing, your weight would be different on another planet, depending on a number of factors including the mass of the planet and how far you are away from the center of the planet.Before we start, it’s important to understand that the kilogram is actually a measurement of your mass. And your mass doesn’t change when you go anywhere in the Universe and experience different amounts of gravity. Your weight is best measured in newtons. But since your bathroom doesn’t measure your weight in newtons, we’ll use kilograms. This is what your bathroom scale would say if you stepped on another world.

Mercury is the smallest planet in our Solar System, but it is dense. Because Mercury is so small, it has very little gravity. If you weighed 68 kg on Earth, you would only weigh 25.7 kg on Mercury. Venus is very close to Earth in size and mass. Venus’ mass is roughly 90% of the mass of the Earth. Thus, it is no surprise that someone would weigh a similar amount on Venus. Someone who weighed 68 kg on Earth would weigh 61.6 kg on Venus.Mars is quite a bit smaller than Earth with only 11% of our planet’s mass. Mars is larger than Mercury, but it is not as dense as the smaller planet. If you weighed 68 kg on Earth then you would weigh 25.6 kg on Mars. Since Pluto was demoted to a dwarf planet, Mars became the planet where you would weigh the least.Jupiter is the largest planet in our Solar System with the most mass. Because of Jupiter’s mass, you would weigh more on that planet than on any other one in our Solar System. If you weighed 68 kg on Earth then you would weigh 160.7 kg on Jupiter, over twice your normal weight. That is if you could actually stand on Jupiter’s surface, which is impossible because it is a gas giant, and gas giants do not have solid surfaces.Saturn is a gas giant best known for its planetary rings system. It is also the second biggest planet in our Solar System. Despite its mass though, the planet has a very low density and a lower gravity than Earth. If you weighed 68 kg on Earth, you would weigh 72.3 kg on Saturn.Uranus is a gas giant without a solid surface. Although Uranus is larger in size than Neptune, it has less mass and therefore less gravity. You would only weigh 60.4 kg on Uranus, if you weighed 68 kg on Earth.Neptune, the last planet in our Solar System, is a gas giant. If you weighed 68 kg on Earth, then you would weigh 76.5 kg on Neptune if you could stand on the planet’s surface.Although the Moon is not a planet, it is one of the few objects that astronauts have actually visited. Because the Moon is so small, it has a low density and low gravity. If you weighed 68 kg on Earth, then you would only weigh 11.2 kg on the Moon."Read more: http://www.universetoday.com/35563/weight-on-other-planets/#ixzz2kinOsv1E

"Weight is the force gravity exerts on an object due to its mass. Mass, roughly, measures an object's inertia, its resistance to being moved or stopped, once it's in motion. Your mass remains constant across the universe (except in certain cases discussed in special relativity , but that is another story), while your weight changes depending on the gravitational forces acting on you, which vary from planet to planet.Newton's Law of Universal Gravitation says that everything that has mass attracts every other thing that has mass, pulling with a force (a) directly proportional to the product of the two objects' masses and (b) inversely proportional to the square of the distance separating their centers.In other words, although gravity increases linearly as objects grow more massive, it decreases exponentially as the distance between them increases (a phenomenon known as an inverse-square law). When calculating surface gravity, that distance refers to the space separating you (on the surface) from the planet's center of mass. This means that a planet's size actually has a greater relative impact on its gravity and on your weight on its surface than does its mass.Written as a formula, Newton's gravitation law looks something like this:F = G((Mm)/r2)Where

r is the distance (m) between the centers of the two masses (the planet's radius).

Without getting too bogged down in the math, we can see that this leads to a surprising result. Take the most massive planet in the solar system, Jupiter, which tips the scales at 316 times the mass of the Earth. You might imagine you would weigh 316 times as much there as here. However, because Jupiter's radius balloons to roughly 11 times as large as Earth's, its gravitational force drops off by a factor of 1/112 at its surface (assuming you could find a way to stand on gas clouds). [Read: Would Humans Born On Mars Grow Taller than Earthlings? ]However, that does not mean that the proportion of Jupiter's gravity to Earth's is 316 / 112. To calculate the ratio between Earth's surface gravity and that of any other celestial body, you must compute them separately using the formula above, and then divide the desired planet's gravitational force by Earth's. We will spare you the work:

Mercury: 0.38

Venus: 0.91

Earth: 1.00

Mars: 0.38

Jupiter: 2.34

Saturn: 1.06

Uranus: 0.92

Neptune: 1.19

Pluto: 0.06

Because weight = mass x surface gravity, multiplying your weight on Earth by the numbers above will give you your weight on the surface of each planet. If you weigh 150 pounds (68 kg.) on Earth, you would weigh 351 lbs. (159 kg.) on Jupiter, 57 lbs. (26 kg.) on Mars and a mere 9 lbs. (4 kg.) on the dwarf planet of Pluto." http://www.livescience.com/33356-weight-on-planets-mars-moon.html

Today we talked about the three kinds of frictional forces: static, sliding, and rolling. Students were asked to share and explain their pictorials of each type of friction (yesterday's homework) on the whiteboard.

We also watched two short video clips. The first was made by the creators of Myth Busters. In it, we discovered the answer to the questions, "When the pages of two books are interlaced, it's possible to pull the books apart. Why?"We watched part of a second clip called the "Rules of Force and Motion" from The Learning Channel. It covered the following questions:

How does the force of gravity keep things grounded?

Why do some celestial bodies orbit others?

How do we overcome inertia?

Homework: Students are to read the first 2 pages of Ch. 11, Section 2 (p. 316-317). In addition, students are to figure out the gravitational constant of our moon and the planet Mercury. With that information, they are to contrast how their weight would be on the moon verses Mercury using the force formula from Newton's Second law of Motion.

Today we had a lively discussion about friction. Friction is one of the natural forces involved in Newton's 1st Law of Motion (also known as the Law of Inertia). There are three kinds of friction: static, sliding, and rolling. We discussed the effects of all three on our daily existence.

Homework: Students are to read 4 pages in their textbook. Re-read pages 310 and 311; then finish reading section one of Chapter 11 (p. 314-315). After reading, they are to create a basic picture rendition of each of the three kinds of friction in their science notebooks. We will share and discuss these in class tomorrow.